This invention relates to an electromagnetic switch for a starter equipped with a switch casing for accommodating a solenoid casing which forms part of a magnetic circuit.
Japanese Patent No. 2973577 discloses a conventional magnet switch for a starter which includes a coil housing (i.e., a solenoid casing) coupled around an outer cylindrical surface of a coil and a starter casing (i.e., a switch casing) having an inside space for accommodating the coil housing. This magnet switch has a plurality of protrusions provided on an outer cylindrical surface of the coil housing or on an inner cylindrical surface of the starter casing. The coil housing is press-fitted into the starter casing, with the protrusions intervening between the coil housing and the starter casing.
However, according to the arrangement of the above-described conventional magnet switch, the circumferential position of the coil housing is arbitrarily changed with respect to the starter casing. The position for taking lead lines out of the coil housing is thus variable relative to the starter casing. It significantly takes a long time to accomplish the work for connecting the lead lines of the coil.
Furthermore, according to the arrangement of the above-described conventional magnet switch, a relatively large clearance remains between the inner cylindrical surface of the starter casing and the outer cylindrical surface of the coil housing. The radial size of the clearance formed between the starter casing and the coil housing is equivalent to the height of the projections. This clearance brings a disadvantage to the above-described conventional magnetic switch in that an available radial space for the coil housing is inevitably reduced due to this clearance in the case the allowable outer diameter of the starter casing is limited to a predetermined value. As a result, the radial size of the coil accommodated in the coil housing is restricted. The coil cannot sufficiently produce a magnetic attraction force.